362 Dr. Faraday's Experimental Researches in Electricity^ xv. 



1759. These conductors being put over the fish, collected 

 power sufficient to produce many electric effects ; but when, 

 as in obtaining the spark, every possible advantage was need- 

 ful, then glass plates were placed at the bottom of the water, 

 and the fish being over them, the conductors were put over it 

 until the lower caoutchouc edges rested on the glass, so that 

 the part of the animal within the caoutchouc was thus almost 

 as well insulated as if the Gymnotus had been in the air. 



1760. Shock. The shock of this animal was very powerful 

 when the hands were placed in a favourable position, i. e. one 

 on the body near the head, and the other near the tail ; the 

 nearer the hands were together within certain limits the less 

 powerful was the shock. The disc conductors (1757.) con- 

 veyed the shock very well when the hands were wetted and 

 applied in close contact with the cylindrical handles ; but 

 scarcely at all if the handles were held in the dry hands in an 

 ordinary way. 



1761. Galvanometer. Using the saddle conductors (1758.) 

 applied to the anterior and posterior parts of the Gymnotus, 

 a galvanometer was readily affected. It was not particularly 

 delicate ; for zinc and platina plates on the upper and lower 

 surface of the tongue did not cause a permanent deflection of 

 more than 25°; yet when the fish gave a powerful discharge 

 the deflection was as much as vSO°, and in one case even 40°. 

 The deflection was constantly in a given direction, the electric 

 current being always from the anterior parts of the animal 

 through the galvanometer wire to the posterior parts. The 

 former were therefore for the time externally positive, and 

 the latter negative. 



1762. Ma/ci?ig a magnet. When a little helix containing 

 twenty-two feet of silked wire wound on a quill was put into 

 the circuit, and an annealed steel needle placed in the helix, 

 the needle became a magnet, and the direction of its polarity 

 in every case indicated a current from the anterior to the 

 posterior parts of the Gymnotus through the conductors used. 



1763. Chemical decompositio7i. Polar decomposition of a 

 solution of iodide of potassium was easily obtained. Three 

 or four folds of paper moistened in the solution (322.) were 

 placed between a platina plate and the end of a wire also of 

 platina, these being respectively connected with the two sad- 

 dle conductors (1758). Whenever the wire was in conjunc- 

 tion with the conductor at the fore part of the Gymnotus, 

 iodine appeared at its extremity ; but when connected with 

 the other conductor none was evolved at the place on the paper 

 where it before appeared. So that here again the direction 

 of the current proved to be the same as that given by the 

 former tests. 



